The proposed longitudinal project aims to clarify the dynamic relationship between homelessness and mental health among mothers and children in New York City. It seeks to understand the degree to which mental illness leads to homelessness, the degree to which homelessness may lead to mental illness in adults and emotional disturbance, health problems, and school problems in children, and the extent to which mental illness hinders the resettlement of those who are homeless. The study will examine shelter use in the context of a number of other indicators of residential instability such as not being a primary tenant or living in substandard or unaffordable housing. The study also investigates the role of other risk factors, such as stressful life events and demographic characteristics, and factors which may protect children and families from risk and foster adaptive outcomes. These protective factors include personal characteristics, coping skills, and supportive relationship with other people, social services, and community ties. The project uses and builds on a rich data set based on in-person interviews with 701 homeless families in New York City and a comparison sample of 524 families drawn from the public assistance case load. All will be followed in administrative records to determine patterns of shelter use over time. In addition, both mothers and children in families who were new entrants to shelter at the initial interview and housed families who had never used shelter will be re-interviewed. Final samples of over 700 mothers and over 1000 children will permit detailed analyses of the role of risk and protective factors in homelessness and residential instability.